[ntp:questions] Loop Frequency and Offset

Dave Hart hart at ntp.org
Tue Sep 27 00:43:46 UTC 2011

2011/9/26 Miguel Gonçalves <mail at miguelgoncalves.com>:
> 2011/9/26 Dave Hart <hart at ntp.org>
>> 2011/9/25 Miguel Gonçalves <mail at miguelgoncalves.com>:
>> > I have a machine running FreeBSD 7.4 and it seems that the CPU clock
>> > runs
>> > too fast or slow (positive offset in loopstats is fast or slow?).
>> ntpd's offset and the frequency compensation are both reported as
>> corrections to the local clock to bring it into alignment with the
>> source(s).  So a positive offset means the clock is behind correct,
>> and a positive frequency correction means the clock runs slower than
>> correct.
> Thanks for all your support to reach a solution for this problem!
> I found out that 180 ppm were the result of the CPU running too fast because
> if I increased the CPU frequency by 180 ppm I would get a even higher
> offset. Am I wrong? It seems I solved the problem as I showed in my previous
> post.

I think you're simply confused.  The FreeBSD sysctl you modified isn't
adjusting the TSC frequency.  It's adjusting FreeBSD's estimate of the
TSC frequency.  I stand by my understanding that a positive frequency
compensation reported by ntpd means the clock's uncompensated rate is

Dave Hart

More information about the questions mailing list